Clean up unused app files

[Kingdutch]

The initial commit to this repository contained some things for applications like Storybook and TailwindCSS that we don't actually want for router development (until we build a full-fledged example that would integrate them).

This PR cleans up those files so that the mental overhead of what is actually relevant to look at/keep track of is reduced :)

[zth]

Awesome, muuch cleaner after this! 😄

[zth]

Merge whenever you want!